Conventionally, as the system for detecting the position of an indicator, such as a finger and a dedicated pen, used for a touch panel etc., various systems such as a resistive film system and an capacitive coupling system (capacitance system) have been proposed, for example. Among them, an indicator position detecting device of the capacitive coupling system is being actively developed in recent years.
As the capacitive coupling system, there are two kinds of systems as roughly classified: the surface type (Surface Capacitive Type) and the projected type (Projected Capacitive Type). The surface type is applied to, e.g., ATM (Automated Teller Machine) etc., and the projected type is applied to, e.g., a cellular phone etc. In both systems, change in the state of capacitive coupling between an electrically-conductive film and an indicator (e.g., finger, capacitive pen, etc.) is detected, and the position of the indicator is detected.
An indicator position detecting device of the capacitive coupling system of the projected type is configured by forming an electrode with a predetermined pattern on a transparent substrate or a transparent film for example, and detects change in the state of capacitive coupling between an indicator and the electrode when the indicator gets close to the device. Conventionally, for the indicator position detecting device of such a system, various techniques for optimizing the configuration thereof have been proposed (refer to, e.g., Patent Documents 1 to 5).
Here, a simple description will be made with reference to a drawing about the operation of an indicator position detecting device of the capacitive coupling system of the cross-point type, which has developed from the capacitive coupling system of the projected type. In FIG. 20, the schematic configuration of a sensor part of the indicator position detecting device of the capacitive coupling system of the cross-point type and the principle of position detection are shown.
In general, a sensor part 300 includes a transmitting conductor group 303 composed of plural transmitting conductors 304 and a receiving conductor group 301 composed of plural receiving conductors 302. An insulating layer is disposed between the transmitting conductor group 303 and the receiving conductor group 301. The transmitting conductor 304 is a conductor extended along a predetermined direction (X-direction in FIG. 20), and the plural transmitting conductors 304 are disposed in parallel and spaced apart from each other by a predetermined interval. Furthermore, the receiving conductor 302 is a conductor that is extended along a direction (Y-direction in FIG. 20) intersecting with the extending direction of the transmitting conductor 304 and has a predetermined shape, and the plural receiving conductors 302 are disposed in parallel and spaced apart from each other by a predetermined interval.
In the sensor part 300 with such a configuration, a predetermined signal is supplied to the predetermined transmitting conductor 304, and a change in the current flowing to the intersection (hereinafter referred to as the “cross-point”) of the predetermined transmitting conductor 304 and the receiving conductor 302 is detected for each cross-point. Such a detection system is generally called the capacitive coupling system of the cross-point type. At the position where an indicator 310 (finger etc.) is placed, a current is partially diverted via the indicator 310. Therefore, the position of the indicator 310 can be detected by detecting the cross-point at which a current change has occurred. Furthermore, in the indicator position detecting device of the capacitive coupling system of the cross-point type, plural cross-points are provided on the sensor part 300 and thus detection of multiple points is possible.
The principle of the position detection of the capacitive coupling system of the cross-point type will be described more specifically. For example, now, consideration will be given to an example in which a predetermined signal is supplied to the transmitting conductor Y6 and the position indicated by the indicator 310 on the transmitting conductor Y6 is detected as shown in FIG. 20. In the state in which the signal is supplied to the transmitting conductor Y6, first, a change in the current flowing through the receiving conductor X1 is detected via an amplifier 305. Subsequently, after a predetermined time, the receiving conductor is switched to X2 and a change in the current flowing through the receiving conductor X2 is detected. This operation is repeated through the receiving conductor XM.
Next, in the state in which switching to, e.g., the transmitting conductor Y7 is made and a signal is supplied thereto, the receiving conductor is sequentially switched and a level change of the signal at the position of each of the cross-points on the transmitting conductor Y7 is obtained via the amplifier 305 in the above-described manner. In this manner, a level change of the signal at the positions of all cross-points is obtained.
In the example shown in FIG. 20, the indicator 310 is placed near the cross-points with the receiving conductors X5 and XM-5 on the transmitting conductor Y6, and thus the current flowing near these cross-points changes. Consequently, the output signal of the amplifier 305 changes at the positions corresponding to the vicinity of the cross-points of the receiving conductors X5 and XM-5 on the transmitting conductor Y6. Therefore, the position of the indicator 310 can be detected based on this signal change.